The phrase "greatest expression" means the most exemplary way to convey or communicate something. It signifies the highest level or ultimate form in which something can be expressed. Full definition
You may believe hugs to be awesome and great expressions of love and positive emotions, but your pooch begs to differ. (samivy.com)
The dogs can be one, two or three colors, often giving the dogs great expression. (dogcare.dailypuppy.com)
«What greater expression of faith in the American experiment than this, what greater form of patriotism is there than the belief that America is not yet finished, that we are strong enough to be self - critical, that each successive generation can look upon our imperfections and decide that it is in our power to remake this nation to more closely align with our highest ideals?» (rachelheldevans.com)